1. Field of the Invention
The present invention relates to a vision-protecting composition with prophylactic and therapeutic activity for diabetes or diabetic complications. More particularly, the present invention relates to a vision-protecting composition with prophylactic and therapeutic activity against diabetes or diabetic complications, comprising calcium, vitamin A, vitamin B, vitamin C and vitamin D and optionally a herb extract selected from among a wolfberry extract, an Astragalus membranaceus extract, a Senna obtusifolia extract, a Polygonatum odoratum var. pluriflorum extract, a Rubus coreanus extract and a combination thereof.
2. Description of the Related Art
Diabetes mellitus is one of the most prevalent chronic adult diseases. With the improvement of standards of living and the Westernization of dietary habits, the onset of diabetes has become increasingly prevalent in Korea. In the body, control of the sugar metabolism resides in a balance between consumption and production of sugar in which insulin and glucagon are typically known to be involved. Depending on these hormones, blood sugar levels vary within certain ranges. Any abnormal action of these hormones leads to a problem with sugar metabolism, typically such as diabetes mellitus (Shepherd P R, Kahn B B: Glucose transporters and insulin action-implications for insulin resistance and diabetes mellitus. N Engl J Med 341: 248-257, 1999).
Diabetes mellitus is a group of metabolic diseases characterized by hyperglycemia resulting from the absolute or relative deficiency of insulin activity. The chronic hyperglycemia of diabetes with the poor regulation of blood sugar is associated with long-term complications including hyperlipidemia, retinopathy, nephropathy and nephrotoxicity, which may even result in death. (American Diabetes Association: Diagnosis and classification of diabetes mellitus. Diabetes Care 27: S5-S10, 2004).
Diabetic retinopathy, a complication of diabetes, is a cause of the loss of vision in adults. Due to an impairment of the blood-retinal barrier with microvascular retinal changes, diabetic retinopathy may progress into proliferative diabetic retinopathy, which can eventually lead to blindness. Active research has been directed toward diabetic retinopathy. Angiogenesis plays an important role in the development of proliferative diabetic retinopathy. In the complex processes of angiogenesis, various kinds of cytokines to and growth factors are involved as previously reported (Lee K W, Kim D J, Park J R et al., J Korean Internal Medicine 67: 607-615, 2004; Liekens S et at, Biochemi Pharmacol 61: 253-270, 2001). In a hypertensive condition induced by diabetes mellitus, a variety of cells are promoted to secrete inflammatory factors, with the induction of lipocytes to form and secrete acute reactive factors. High blood sugar and its oxides cause damage to the eyes, the kidneys and vascular cells and the inflammatory factors penetrate into the damaged regions, thus causing damage to more cells. The role of inflammatory factors in the development of complications of diabetes is already known. Recent reports had it that inflammatory factors are associated with the onset of microvascular complications such as microalbuminuria and diabetic retinitis, as well as macrovascular complications such as cardiovascular diseases (Gomes M B, Nogueira V G, Diabetes Research and Clinical Practice 66: 31-39, 2004; Kenneth E. et al., Diabetes Care 28: 714-715, 2005).
T helper cells function to regulate and activate a variety of immune responses. Proliferating helper T cells that develop into effector T cells differentiate into Th1 and Th2 cells. They express their characteristic cytokines that are responsible for different immune functions. Immune homeostasis may be defined as a balance between Th1 and Th2 cells. The onset of a certain immune disease is such that the immune imbalance incurred with the collapse of Th1/Th2 balance induces immune diseases of each T helper type. Inadequate Th1 immune responses account for autoimmune diseases such as rheumatoid and diabetes while hypersensitive Th2 immune responses result in allergy and asthma.
On the basis of accurate understanding of the etiology and pathophysiology of diabetes mellitus, molecular biological studies have recently been actively performed to develop improved therapeutics overcoming the limitations of conventional ones. Against the background of these studies, various transcription factors are suggested as theoretical bases for the development of new drugs. In practice, research results have been reported that have focused on immunoregulators, inflammatory factors, growth factors, cytokines and the like. In addition, complications of diabetes mellitus, rather than diabetes mellitus itself, are under active study because they are more serious in many cases (Jeon, Young Jin, The Korean Society for Microbiology and Biotechnology, Trends of Research into Complications of Diabetes Mellitus, Pharmacology Class, College of Medicine, Chosun University).
However, a velar interrelationship has to be proven between various signal transmitters, growth factors, cytokines, immune regulators, and inflammatory factors in the abnormality of sugar metabolisms and the onset of diabetes and diabetic complications. Particularly, studies on diabetic retinopathy remain only slightly advanced.